CN112358872B - Nitrogen-boron co-doped carbon quantum dot and application thereof in high-sensitivity detection of cadmium ions - Google Patents

Nitrogen-boron co-doped carbon quantum dot and application thereof in high-sensitivity detection of cadmium ions Download PDF

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CN112358872B
CN112358872B CN202011237301.8A CN202011237301A CN112358872B CN 112358872 B CN112358872 B CN 112358872B CN 202011237301 A CN202011237301 A CN 202011237301A CN 112358872 B CN112358872 B CN 112358872B
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刘意
严志红
姚微
徐丽
孙福强
何洋
杨帆
刘天宇
李梓权
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Abstract

The invention relates to the field of quantum dots, in particular to a nitrogen and boron co-doped carbon quantum dot and application thereof in high-sensitivity detection of cadmium ions. The method selects proper carbon source, nitrogen source and boron source and proper proportion, and the nitrogen-boron co-doped carbon quantum dot prepared by a one-step hydrothermal method has proper fluorescence intensity and sensitive Cd 2+ Responsiveness and selectivity, can be used for Cd in solution 2+ And (4) detecting the concentration.

Description

Nitrogen-boron co-doped carbon quantum dot and application thereof in high-sensitivity detection of cadmium ions
Technical Field
The invention relates to the field of quantum dots, in particular to a nitrogen and boron co-doped carbon quantum dot, a preparation method thereof and application thereof in high-sensitivity detection of cadmium ions.
Background
Carbon Quantum Dots (CQDs) have many unique advantages over organic dyes and conventional semiconductor quantum dots, including good solubility in aqueous solutions, low toxicity, good biocompatibility and environmental friendliness, and good sensitivity and selectivity. In addition, carbon dots have been widely used in a wide range of fields such as bio-imaging, catalysis, and sensors. Previous studies have demonstrated that both surface functionalization/passivation and heteroatom doping can improve the performance of CQDs in the above applications.
Pollution caused by various heavy metal ions has become a worldwide significant problem threatening human health and ecosystem. Among the heavy metal ions, cadmium ion (Cd) 2+ ) Has proved to be a highly toxic heavy metal ion, and has wide application in the weapon industry, metallurgy electroplating and agriculture. Phagocytosis of contaminated food or water by continuous exposure to trace amounts of Cd 2+ People with ionic ions can cause serious damage to the lung, kidney, bone, nervous system, and even some cancers. Thus, for Cd 2+ Is very necessary.
Common detection of Cd 2+ Examples of the method of the ion include atomic absorption spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), spectrophotometry, and stripping voltammetry. Although these methods have high sensitivity and multiplex detection capability, the complex sample preparation process and the high cost, high time detection process limit their application in many practical cases. Therefore, the development of a method capable of selectively and sensitively detecting Cd 2+ Simple methods of ion implantation are at hand.
In recent years, fluorescent sensors have attracted much attention due to their advantages of simplicity, economy, high sensitivity, intuition, fast response, and the like. To date, various fluorescent probes have been developed that rely on organic dye molecules, metal nanoparticles, and semiconductor Quantum Dots (QDs). However, most of these probes are either toxic or have low sensitivity and poor selectivity.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a method for detecting Cd based on the fluorescence enhancement effect of carbon quantum dots 2+ The method takes the nitrogen and boron co-doped carbon quantum dots synthesized by the one-step hydrothermal method as the fluorescent probe, has the advantages of simple synthesis method, quick and convenient detection and accurate result, and solves the problems of high equipment cost, complex operation, environmental hazard and the like of the traditional cadmium ion detection method. In order to achieve the above purpose, the invention provides the following technical scheme:
a nitrogen and boron co-doped carbon quantum dot (N, B-CQDs) is prepared from the following raw materials:
a carbon source, a nitrogen source, and a boron source; wherein the nitrogen source is selected from a compound taking 2-amino-3-hydroxypyridine as a mother nucleus and has a structure shown in a formula I,
Figure BDA0002767145600000021
wherein R is 1 、R 2 And R 3 Each independently selected from H, methyl, ethyl, propyl, isopropyl, amino or carboxyl.
Further, said R 2 Is H.
Further, said R 1 、R 2 And R 3 Are all hydrogen.
Further, the carbon source is selected from citric acid.
Further, the nitrogen source is selected from 2-amino-3-hydroxypyridine.
Further, the boron source is selected from at least one of sodium borohydride, boric acid, and a borate.
Further, the borate is selected from at least one of sodium borate and hydrated sodium borate.
Furthermore, the raw materials comprise, by weight, 0.8-1.2 parts of a carbon source, 0.18-0.5 part of a nitrogen source and 0.1-0.3 part of a boron source.
A preparation method of nitrogen and boron co-doped carbon quantum dots (N, B-CQDs) comprises the following steps:
1) dissolving a carbon source, a nitrogen source and a boron source in pure water to obtain a solution A;
2) heating the solution A for reaction to obtain a solution B;
3) dialyzing the solution B to obtain a solution C;
4) and carrying out suction filtration and drying on the solution C to obtain powdery N, B-CQDs.
Further, the reaction temperature of the solution A in the step 2) is 150-180 ℃, and the reaction time is 90-300 min.
Further, the reaction temperature of the solution A in the step 2) is 180 ℃, and the reaction time is 150 min.
Further, the dialysis treatment in the step 3) is carried out in the dialysis bag of 800D-1200D, and the dialysis time is 24-72 h.
The application of the nitrogen and boron co-doped carbon quantum dot is in Cd 2+ Application in detection.
Applying the nitrogen and boron co-doped carbon quantum dots to Cd 2+ A method in assay comprising the steps of:
1) dissolving the N, B-CQDs in ultrapure water to prepare a solution D, and testing the fluorescence intensity of the solution D, which is marked as F 0 ；
2) Respectively mixing the cadmium ion solutions with different concentrations with the solution D to respectively obtain mixed solutions, and performing fluorescence test on the mixed solutions to respectively obtain fluorescence intensity values of the mixed solutions, and recording the fluorescence intensity values as F;
3) calculating the fluorescence increase rate y ═ F/F 0 -1；
4) Taking the concentration of cadmium ions as an abscissa and the fluorescence growth rate as an ordinate, and performing linear fitting to obtain a regression equation y ═ f (x), wherein y is the fluorescence growth rate, x is the concentration of cadmium ions, k is a slope, and b is an intercept;
5) mixing the solution containing cadmium ions to be detected with the solution D, and incubating at room temperature for 3min-10min to obtain a Cd/N, B-CQDs mixed solution; and (3) performing fluorescence test to obtain fluorescence intensity, calculating the fluorescence increase rate of the Cd/N and B-CQDs mixed solution, substituting the fluorescence increase rate into a linear regression equation y ═ f (x), and calculating to obtain the concentration of cadmium ions.
Further, the mass concentration of the solution D in the step 1) is 0.1-1mg/ml, and preferably 0.1 mg/ml.
Further, the concentration of different cadmium ions in the step 2) is 2.5-250 μ M.
Further, the concentration of different cadmium ions in the step 2) is 2.5-25 μ M.
The invention has the advantages that:
1. the doped carbon quantum dots containing pyridine rings are hydrothermally synthesized by a one-step method by using the designed raw material formula system, and the fluorescence characteristics (fluorescence enhancement effect, intensity enhancement can reach as high as that of the carbon quantum dots) are utilized200％F 0 ) As a fluorescent probe, provides a method for detecting Cd by using fluorescence enhancement effect 2+ The method of (1).
2. The method is characterized in that a boron and nitrogen doped carbon quantum dot is synthesized by taking a 2-amino-3-hydroxypyridine mother nucleus as a nitrogen source and sodium borohydride, boric acid or borate as a boron source.
3. The carbon quantum dots prepared by the technical scheme of the invention have the advantages of simple synthesis method, easy mass production and small harm to the environment; the product has the advantages of stable physical and chemical properties, good water solubility, high fluorescence intensity, high quantum yield, specific selective responsiveness to cadmium ions, high sensitivity and the like.
4. The cadmium ion content detection scheme based on the quantum dots has the advantages of high sensitivity, less spectral interference, lower cost and the like, is based on the fluorescence enhancement effect, is different from most schemes for detecting heavy metal ions based on the carbon quantum dot fluorescence quenching effect in the market, and has innovation.
Drawings
FIG. 1 example 1 of products N, B-CQDs 1 H-NMR；
FIG. 2 is a chart of the infrared absorption spectra of N, B-CQDs, the product of example 1;
FIG. 3 fluorescence emission spectra of the products of examples 1-9;
FIG. 4 fluorescence intensity at 420nm for the products of examples 1-9;
FIG. 5 fluorescence response of the product of example 1 to different ions;
FIG. 6 examples 1-9 on Cd 2+ The fluorescence enhancing property of (a);
FIG. 7 comparison of product pair Cd in example 1 2+ The fluorescence response spectrum of (a);
FIG. 8 comparison of product pair Cd in example 2 2+ The fluorescence response spectrum of (a);
FIG. 9 product of example 1 in aqueous solution for different concentrations of Cd 2+ (ii) a responsive fluorescence emission spectrum;
FIG. 10 fluorescence intensity variation and Cd for the product of example 1 2+ The relationship between the concentrations.
Detailed Description
The specific implementation steps of the invention are mainly divided into two steps, wherein the first step is to synthesize the carbon quantum dots, and the carbon quantum dots are properly purified and then freeze-dried for later use; and the second step is to prepare an aqueous solution with proper concentration by using the synthesized carbon quantum dot material, then add a certain amount of sample containing cadmium ions, and analyze and detect the concentration of the cadmium ions by using a fluorescence spectrometry.
The first step of synthesizing doped carbon quantum dots (N, B-CQDs) comprises the following synthetic route: carrying out hydrothermal reaction on a synthetic formula of a carbon source, a nitrogen source and a boron source carbon quantum dot at the temperature of 150-180 ℃ for 90-300min, purifying the obtained crude product, and freeze-drying for later use.
The specific implementation is as follows:
the preparation method of the carbon quantum dots comprises the following specific steps:
example 1
1) Sequentially dissolving 0.84g of citric acid, 0.5g of 2-amino-3-hydroxypyridine and 0.08g of sodium borohydride in 30mL of pure water to obtain a solution A;
2) transferring the solution A into a polytetrafluoroethylene lining, and then putting the polytetrafluoroethylene lining into a stainless steel reaction kettle to react for 150min at 180 ℃ to obtain a solution B;
3) transferring the solution B into a dialysis bag of 1000D, and dialyzing for 48h to obtain a solution C;
4) and (3) carrying out suction filtration on the solution C by using a 0.45-micron organic filter membrane, freezing for 4h at-60 ℃, extracting and vacuum-drying for 12h to obtain brown powdery D (N, B-CQDs), and storing at 0 ℃ for later use.
The D prepared in this example (carbon quantum dots N, B-CQDs doped with nitrogen and boron, NMR spectrum shown in figure 1, and infrared absorption spectrum shown in figure 2) is a tan powder which is very soluble in water. Because the surface of the metal ion fluorescent material contains a large number of hydroxyl, carboxyl and pyridine rings, the functional groups can interact with cadmium ions, so that N, B-CQDs solution with a certain concentration has high-intensity fluorescence, and specific metal ions (such as cadmium ion Cd) 2+ ) High sensitivity detection of (1).
Example 2
Preparation method of carbon Quantum dot referring to example 1, reaction raw material m Citric acid +m 2-amino-3-hydroxyPyridine compound The sum is kept unchanged, but the proportion is changed correspondingly, and the specific steps are as follows:
1) dissolving 1g of citric acid, 0.343g of 2-amino-3-hydroxypyridine and 0.08g of sodium borohydride in 30mL of pure water to obtain a solution A;
2) transferring the solution A into a polytetrafluoroethylene lining, and then putting the polytetrafluoroethylene lining into a stainless steel reaction kettle to react for 150min at 180 ℃ to obtain a solution B;
3) transferring the solution B into a dialysis bag of 1000D, and dialyzing for 48h to obtain a solution C;
4) and (3) carrying out suction filtration on the solution C by using a 0.45-micron organic filter membrane, freezing for 4h at-60 ℃, extracting and vacuum-drying for 12h to obtain brown powdery D (N, B-CQDs), and storing at 0 ℃ for later use.
Example 3
Preparation method of carbon Quantum dot referring to example 1, reaction raw material m Citric acid +m 2-amino-3-hydroxypyridines The sum is kept unchanged, but the proportion is changed correspondingly, and the specific steps are as follows:
1) dissolving 1.16g of citric acid, 0.183g of 2-amino-3-hydroxypyridine and 0.08g of sodium borohydride in 30mL of pure water to obtain a solution A;
2) transferring the solution A into a polytetrafluoroethylene lining, and then putting the polytetrafluoroethylene lining into a stainless steel reaction kettle to react for 150min at 180 ℃ to obtain a solution B;
3) transferring the solution B into a dialysis bag of 1000D, and dialyzing for 48h to obtain a solution C;
4) and (3) carrying out suction filtration on the solution C by using a 0.45-micron organic filter membrane, freezing for 4h at-60 ℃, extracting and vacuum-drying for 12h to obtain brown powdery D (N, B-CQDs), and storing at 0 ℃ for later use.
Example 4
Referring to example 3, the amounts of citric acid and 2-amino-3-hydroxypyridine used as reaction raw materials are kept unchanged, and the amount of the B source is changed, and the specific steps are as follows:
1) dissolving 1.16g of citric acid, 0.183g of 2-amino-3-hydroxypyridine and 0.133g of sodium borohydride in 30mL of pure water to obtain a solution A;
2) transferring the solution A into a polytetrafluoroethylene lining, and then putting the polytetrafluoroethylene lining into a stainless steel reaction kettle to react for 150min at 180 ℃ to obtain a solution B;
3) transferring the solution B into a dialysis bag of 1000D, and dialyzing for 48h to obtain a solution C;
4) filtering the solution C with 0.45 μm organic filter membrane, freezing at-60 deg.C for 4 hr, vacuum drying for 12 hr to obtain brown powder D (N, B-CQDs), and storing at 0 deg.C.
Example 5
Referring to example 1, the preparation method of the carbon quantum dot only changes the amount of sodium borohydride, and comprises the following specific steps:
1) dissolving 0.84g of citric acid, 0.5g of 2-amino-3-hydroxypyridine and 0.3g of sodium borohydride in 30mL of pure water to obtain a solution A;
2) transferring the solution A into a polytetrafluoroethylene lining, and then putting the polytetrafluoroethylene lining into a stainless steel reaction kettle to react for 150min at 180 ℃ to obtain a solution B;
3) transferring the solution B into a dialysis bag of 1000D, and dialyzing for 48h to obtain a solution C;
4) filtering the solution C with 0.45 μm organic filter membrane, freezing at-60 deg.C for 4 hr, vacuum drying for 12 hr to obtain brown powder D (N, B-CQDs), and storing at 0 deg.C.
Example 6
Referring to example 1, the preparation method of the carbon quantum dot comprises the following specific steps of changing a B source into sodium borohydride with equal mass of boric acid:
1) dissolving 0.84g of citric acid, 0.5g of 2-amino-3-hydroxypyridine and 0.133g of boric acid in 30mL of pure water in sequence to obtain a solution A;
2) transferring the solution A into a polytetrafluoroethylene lining, and then putting the polytetrafluoroethylene lining into a stainless steel reaction kettle to react for 150min at 180 ℃ to obtain a solution B;
3) transferring the solution B into a dialysis bag of 1000D, and dialyzing for 48h to obtain a solution C;
4) and (3) carrying out suction filtration on the solution C by using a 0.45-micron organic filter membrane, freezing for 4h at-60 ℃, extracting and vacuum-drying for 12h to obtain brown powdery D (N, B-CQDs), and storing at 0 ℃ for later use.
Example 7
Referring to example 1, the preparation method of the carbon quantum dots adopts borax with equal mass obtained by changing B source into sodium borohydride, and comprises the following specific steps:
1) dissolving 0.84g of citric acid, 0.5g of 2-amino-3-hydroxypyridine and 0.133g of borax in 30mL of pure water in sequence to obtain a solution A;
2) transferring the solution A into a polytetrafluoroethylene lining, and then putting the polytetrafluoroethylene lining into a stainless steel reaction kettle to react for 150min at 180 ℃ to obtain a solution B;
3) transferring the solution B into a dialysis bag of 1000D, and dialyzing for 48h to obtain a solution C;
4) and (3) carrying out suction filtration on the solution C by using a 0.45-micron organic filter membrane, freezing for 4h at-60 ℃, extracting and vacuum-drying for 12h to obtain brown powdery D (N, B-CQDs), and storing at 0 ℃ for later use.
Example 8
Referring to example 1, the method for preparing the carbon quantum dots includes the following steps that the dosage of sodium borohydride is changed by a B source:
1) dissolving 0.84g of citric acid, 0.5g of 2-amino-3-hydroxypyridine and 0.16g of sodium borohydride in 30mL of pure water in sequence to obtain a solution A;
2) transferring the solution A into a polytetrafluoroethylene lining, and then putting the polytetrafluoroethylene lining into a stainless steel reaction kettle to react for 150min at 180 ℃ to obtain a solution B;
3) transferring the solution B into a dialysis bag of 1000D, and dialyzing for 48h to obtain a solution C;
4) filtering the solution C with 0.45 μm organic filter membrane, freezing at-60 deg.C for 4 hr, vacuum drying for 12 hr to obtain brown powder D (N, B-CQDs), and storing at 0 deg.C.
Example 9
Referring to example 1, the method for preparing the carbon quantum dots includes the following steps that the dosage of sodium borohydride is changed by a B source:
1) dissolving 0.84g of citric acid, 0.5g of 2-amino-3-hydroxypyridine and 0.04g of sodium borohydride in 30mL of pure water in sequence to obtain a solution A;
2) transferring the solution A into a polytetrafluoroethylene lining, and then putting the polytetrafluoroethylene lining into a stainless steel reaction kettle to react for 150min at 180 ℃ to obtain a solution B;
3) transferring the solution B into a dialysis bag of 1000D, and dialyzing for 48h to obtain a solution C;
4) and (3) carrying out suction filtration on the solution C by using a 0.45-micron organic filter membrane, freezing for 4h at-60 ℃, extracting and vacuum-drying for 12h to obtain brown powdery D (N, B-CQDs), and storing at 0 ℃ for later use.
Comparative example 1
Referring to example 1, the preparation method of the carbon quantum dot takes ethylene diamine with equal mass as a nitrogen source, and comprises the following specific steps:
1) sequentially dissolving 0.84g of citric acid, 0.5g of ethylenediamine and 0.08g of sodium borohydride in 30mL of pure water to obtain a solution A;
2) transferring the solution A into a polytetrafluoroethylene lining, and then putting the polytetrafluoroethylene lining into a stainless steel reaction kettle to react for 150min at 180 ℃ to obtain a solution B;
3) transferring the solution B into a dialysis bag of 1000D, and dialyzing for 48h to obtain a solution C;
4) filtering the solution C with 0.45 μm organic filter membrane, freezing at-60 deg.C for 4 hr, vacuum drying for 12 hr to obtain brown powder D (N-CQDs), and storing at 0 deg.C.
Comparative example 2
Referring to example 1, the preparation method of the carbon quantum dot uses 3-aminopyridine with equal mass as a nitrogen source and comprises the following specific steps:
1) sequentially dissolving 0.84g of citric acid, 0.5g of 3-aminopyridine and 0.08g of sodium borohydride in 30mL of pure water to obtain a solution A;
2) transferring the solution A into a polytetrafluoroethylene lining, and then putting the polytetrafluoroethylene lining into a stainless steel reaction kettle to react for 150min at 180 ℃ to obtain a solution B;
3) transferring the solution B into a dialysis bag of 1000D, and dialyzing for 48h to obtain a solution C;
4) filtering the solution C with 0.45 μm organic filter membrane, freezing at-60 deg.C for 4 hr, vacuum drying for 12 hr to obtain brown powder D (N-CQDs), and storing at 0 deg.C.
Test examples-product pairs of examples and comparative examples Cd 2+ Response performance
The products of examples 1 to 9 and comparative examples 1 to 2 were each dissolved in ultrapure water to prepare a 0.1mg/mL quantum dot solution.
Experiment 1): the solutions prepared from the products of examples 1 to 9 were used to measure fluorescence emission spectra with 360nm excitation light, respectively, to obtain FIG. 3.
Experiment 2): the fluorescence intensity values at 420nm of the products of examples 1-9 were taken from FIG. 3 and plotted in FIG. 4.
Experiment 3): respectively taking the carbon quantum dot solution prepared by the product of the example 1, and respectively adding Cd into the carbon quantum dot solution 2+ 、Cr 6+ 、Cr 3+ 、Fe 3+ 、Cu 2+ 、Ba 2+ 、Mg 2+ 、Ni 2+ 、Mn 2+ 、Pd 2+ Or Hg 2+ Corresponding water-soluble inorganic salt is prepared into a solution with 0.1mg/mL of carbon quantum dots and 30 mu M of metal ions, 360nm is respectively used as exciting light, a fluorescence emission spectrum is tested, and the fluorescence intensity at 420nm is selected to obtain a graph 5.
Experiment 4): the carbon quantum dot solutions prepared from the products of examples 1-9 were taken separately and Cd was added 2+ Corresponding water-soluble inorganic salt is prepared into 0.1mg/mL of carbon quantum dots and Cd 2+ 30 μ M solution, respectively using 360nm as exciting light, fluorescence emission spectra were measured, and the fluorescence intensity at 420nm was selected, to obtain FIG. 6.
Experiment 5): adding Cd into a carbon quantum dot solution prepared from the product of the comparative example 1 2+ Corresponding water-soluble inorganic salt is prepared into 0.1mg/mL of carbon quantum dots and Cd 2+ The fluorescence emission spectrum was measured for 250. mu.M solution with 360nm excitation light, and FIG. 7 was obtained.
Experiment 6): taking the carbon quantum dot solution prepared from the product of comparative example 2, adding Cd 2+ Corresponding water-soluble inorganic salt is prepared into 0.1mg/mL of carbon quantum dots and Cd 2+ The fluorescence emission spectrum was measured using a 250. mu.M solution and 360nm as excitation light, and FIG. 8 was obtained.
Experiment 7):
the powdery D (N, B-CQDs) obtained in example 1 was dissolved in ultrapure water to prepare a 0.1mg/mL solution of D, and the fluorescence intensity was measured and recorded as F 0 ；
1) The concentrations of 2.5. mu.M, 5. mu.M, 7.5. mu.M, 10. mu.M, 12.5. mu.M, 15. mu.M, 17.5. mu.M,20 μ M, 22.5 μ M, 25 μ M, 50 μ M, 100 μ M, 150 μ M, 200 μ M or 250 μ M Cd 2+ Respectively mixing the solution with the solution D to respectively obtain mixed solutions, and performing fluorescence test on the mixed solutions to respectively obtain fluorescence intensity values of the mixed solutions, and marking the fluorescence intensity values as F;
the increase rate of fluorescence (F/F) with the concentration of cadmium ion as the abscissa x 0 -1) taking an ordinate y, and performing linear fitting to obtain a regression equation y ═ f (x), wherein y is a fluorescence growth rate, x is a concentration of cadmium ions, k is a slope, and b is an intercept;
2) mixing the solution containing cadmium ions to be detected with the solution D, and incubating at room temperature for 3min-10min to obtain a Cd/N, B-CQDs mixed solution; and (3) performing fluorescence test to obtain the fluorescence intensity value of the Cd/N, B-CQDs mixed solution, substituting the fluorescence intensity value into a linear regression equation y ═ f (x), and calculating to obtain the concentration of cadmium ions.
The fluorescence intensity value test takes 360nm as exciting light, and selects the fluorescence intensity at 420nm as the fluorescence intensity value of the tested solution.
The fitting equation obtained in this experiment is shown in the following formula:
Figure BDA0002767145600000081
wherein, when x is more than or equal to 0 and less than 50, R is 0.9918; when x is more than or equal to 50 and less than or equal to 250, R is 0.9532.
The test results are shown in fig. 9 and 10. It can be seen that the fitted two-piece linear equation R>0.95, has better fitting effect, and shows that the carbon quantum dots provided by the invention have a good fitting effect on 0-250 mu M Cd 2+ Can have more accurate detection effect.
Comparing the fluorescence intensities of the aqueous solutions of the same concentration of product D obtained in the above examples, it was found that examples 1 to 9 all have stronger fluorescence emission intensities (FIG. 3, FIG. 4); example 1 of the same concentration in solutions of different metal ions of the same concentration, only Cd 2+ On which there is a fluorescence enhancing effect, the description of example 1 on Cd 2+ Has better selectivity (figure 5); at the same time, Cd 2+ Has stronger fluorescence enhancement effect on examples 1-9, which reaches more than 1.4 times, especially on experimentsThe product of example 1 showed a 2-fold increase in fluorescence (FIG. 6). Illustrative examples 1-9 all had the detection of Cd 2+ The potential of (2).
According to the results of FIG. 5, due to Fe 3+ 、Cu 2+ 、Ni 2+ 、Pb 2+ 、Hg 2+ Has stronger fluorescence inhibition effect on the quantum dots, so the invention also tests Cd under the condition of the existence of the ions 2+ The interference on the fluorescence enhancement effect of the carbon quantum dots of the invention discovers that Cd is generated even if other ions exist 2+ The carbon quantum dots still have strong fluorescence enhancement effect.
In the performance tests of comparative examples 1-2, it was found that both were paired with Cd 2+ No obvious response is shown (fig. 7, fig. 8), which shows that the 2-amino-3-hydroxypyridine is necessary as the parent nucleus for preparing the carbon quantum of the invention.
It should be noted that the carbon quantum dot prepared by the method provided by the invention has the carbon quantum dot and Cd by using the 2-amino-3-hydroxypyridine parent nucleus compound as the nitrogen source of the carbon quantum dot 2+ The specific embodiment of the present invention using 2-amino-3-hydroxypyridine merely as an example to illustrate the problem to be solved by the present invention, it will be understood by those skilled in the art that when R is 1 、R 2 、R 3 When each is independently selected from H, methyl, ethyl, propyl, isopropyl, amino or carboxyl, the generation of the specific structure is not influenced, and the para-Cd can be obtained 2+ The effect of the response.
Finally, it should be noted that the above-mentioned contents are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, and that the simple modifications or equivalent substitutions of the technical solutions of the present invention by those of ordinary skill in the art can be made without departing from the spirit and scope of the technical solutions of the present invention.

Claims (8)

1. A nitrogen and boron co-doped carbon quantum dot in Cd 2+ The application in detection and the preparation method of the carbon quantum dot comprise the following steps:
1) dissolving a carbon source, a nitrogen source and a boron source in pure water to obtain a solution A; wherein the carbon source is selected from citric acid; the nitrogen source is selected from 2-amino-3-hydroxypyridine; the boron source is selected from at least one of borohydride, boric acid and borate;
2) heating the solution A for reaction to obtain a solution B;
3) dialyzing the solution B to obtain a solution C;
4) filtering and drying the solution C to obtain powdery nitrogen and boron co-doped carbon quantum dots (N, B-CQDs);
the reaction temperature of the solution A in the step 2) is 150-180 ℃, and the reaction time is 90-300 min.
2. The use of claim 1, wherein the borate salt is selected from at least one of sodium borate and hydrated sodium borate.
3. The use according to claim 1, wherein the carbon source is 0.8-1.2 parts, the nitrogen source is 0.18-0.5 parts, and the boron source is 0.1-0.3 parts by weight.
4. The use according to claim 1, wherein the reaction temperature of solution A in step 2) is 180 ℃ and the reaction time is 150 min.
5. Use according to claim 1, wherein the dialysis treatment in step 3) is carried out in a dialysis bag of 800D-1200D for a dialysis time of 24-72 h.
6. The use of any one of claims 1-3, wherein the nitrogen and boron co-doped carbon quantum dots are used for detecting Cd 2+ A method of concentration comprising the steps of:
A) the N, B-CQDs were dissolved in ultrapure water to prepare a solution D, and the fluorescence intensity thereof was measured and designated as F 0 ；
B) Respectively mixing the cadmium ion solutions with different concentrations with the solution D to respectively obtain mixed solutions, and performing fluorescence test on the mixed solutions to respectively obtain fluorescence intensity values of the mixed solutions, and recording the fluorescence intensity values as F;
C) calculating the fluorescence growth rate y = F/F 0 -1；
D) Taking the concentration of cadmium ions as an abscissa and the fluorescence growth rate as an ordinate, and performing linear fitting to obtain a regression equation y ═ f (x), wherein y is the fluorescence growth rate, x is the concentration of cadmium ions, k is the slope, and b is the intercept;
E) mixing the solution containing cadmium ions to be detected with the solution D, and incubating at room temperature for 3min-10min to obtain a Cd/N, B-CQDs mixed solution; and (3) performing fluorescence test to obtain fluorescence intensity, calculating the fluorescence increase rate of the Cd/N and B-CQDs mixed solution, substituting the fluorescence increase rate into a regression equation y ═ f (x), and calculating to obtain the concentration of cadmium ions.
7. The use according to claim 6, wherein the solution D of step A) has a mass concentration of 0.1 to 1 mg/ml; the concentration of the cadmium ion solution with different concentrations in the step B) is 0-250 mu M.
8. The use of claim 6, wherein the concentration of the different concentrations of cadmium ion solution of step B) is 0-50 μ M.
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